Almost as old as the Fischer-Tropsch process for making hydrocarbons is the Fischer-Tropsch process for making alcohols. The reaction is carried out by passing a mixture of carbon monoxide and hydrogen over a catalyst for the hydrogenation of the carbon monoxide. A typical review article is R. B. Anderson et al., Industrial and Engineering Chemistry, Vol. 44, No. 10, pp. 2418-2424. This paper lists a number of catalysts containing zinc, copper, chromium, manganese, thorium, iron, occasionally promoted with alkali or other materials for making various alcohols. The authors state that ethyl alcohol is a major constituent, the yield of methanol is usually very small and a tentative summary of factors favoring the production of alcohols are high pressure, low temperature, high space velocity, high recycle ratio and carbon monoxide-rich synthesis gas.
Molybdenum is known to be catalytic for the Fischer-Tropsch process and is taught in U.S. Pat. Nos. 4,151,190 and 4,199,522 which are incorporated herein by reference. The references describe some of the herein used catalysts but do not teach that the catalysts are useful for making commercially significant quantities of alcohols.
U.S. Pat. No. 2,490,488 discloses that molybdenum sulfide methanation catalysts acquire Fischer-Tropsch activity when promoted with an alkaline compound of an alkali metal. The example of the invention shows a 30% selectivity to C.sub.3 + hydrocarbons and oxygenates. Of this 30%, no more than 44% boils near or above 65.degree. C. the boiling point of methanol. Accordingly the maximum possible alcohol selectivity is no more than 13.2% (44% of 30%).
U.S. Pat. No. 2,539,414 describes a Fischer-Tropsch process with molybdenum carbide catalysts. It teaches that the catalyst may be used to form oxygenates and at column 3, lines 66-71 teaches that one might get alcohols or hydrocarbons by varying the conditions.
G. T. Morgan et al., J. Soc. Chem. Ind., Vol. 51, 1932 Jan. 8, pp. 1T-7T, describe a process for making alcohols with chromium/manganese oxide catalysts promoted with alkali.
A number of references teach production of alcohols using rhodium catalysts. Some of these contain molybdenum as an optional ingredient. U.S. Pat. No. 4,014,913 discloses a catalyst containing rhodium and thorium or uranium and iron or molybdenum or tungsten for the production of ethanol. U.S. Pat. No. 4,096,164 discloses the use of rhodium in combination with molybdenum or tungsten and Example A discloses that use of a molybdenum-on-silica catalyst yielded 4.4 percent oxygenates.
EPO application No. 81-33,212 (Chemical Abstracts 96: 51,800a) discloses a similar process using rhodium in combination with one or more of a long list of metals which includes molybdenum.
EPO application No. 79-5,492 (Chemical Abstracts 92: 166,257b), Hardman et al., discloses the production of alcohols using a 4-component catalyst. The first component is copper, the second is thorium, the third an alkali metal promoter and the fourth a long list of metals one of which is molybdenum. Chemical Abstracts 96: 106,913x, Diffenbach et al., disclose a nitrided iron catalyst which is promoted with molybdenum for making alcohols from synthesis gas.
All of the aforementioned references are hereby incorporated by reference.
To make a commercially significant alcohol process, one must use a catalyst and conditions which are highly efficient. To be efficient the catalyst must yield a high ratio of mass of product per given mass of catalyst in a given period of time. The catalyst must be stable and active for long periods of time between regenerations. This may be particularly difficult to accomplish when the H.sub.2 /CO ratio of the feed gas is low, such as less than 2 to 1. Ideally the catalyst will have a high selectivity to a commercial product to avoid purification or removal and disposal of by-products and to avoid separation into two or more product streams.